Syncope refers to a sudden loss of consciousness often accompanied with collapse, more commonly known as a blackout or faint.

Syncope is caused by a lack of blood or oxygen to the brain. When this happens, the brain attempts to increase blood flow to itself by diverting blood away from the rest of the body. This causes pale skin and a white face, rapid heart rate (tachycardia), rapid breathing (hyperventilation) and weakness of the limbs, particularly the legs. Eventually collapse occurs.

What can induce syncope?

There are a number of situations that can induce syncope. Too little food or water, low blood sugar (hypoglycaemia), intense physical exercise, and standing up too quickly can all cause an episode of fainting. Additionally, low blood pressure (hypertension) and an abnormal heart rhythm (arrhythmia) can also cause a lack of blood to the brain and induce syncope.

Who can suffer from syncope?

Syncope can occur in anyone.

What risks are associated with syncope?

Infrequent, one-off syncope episodes are not thought to be serious but it is important to remember that sudden collapse can be a frightening and often embarrassing situation. The potential for injury upon collapse is also high. Generally, recovery is quick from a few minutes to up to an hour.

Recurrent episodes of syncope may be a sign of a more serious underlying condition and require further investigation.

How is syncope investigated?

Simple syncope episodes can be diagnosed fairly easily by a doctor without complicated tests. However, recurrent episodes may be a symptom of another condition and a specialist doctor may order some tests to investigate what could be the cause of syncope.

Very often a specialist consultation with a 12 lead Electrocardiogram will point to a diagnosis, but other tests may be needed such as an ambulatory 24 hourelectrocardiogram, electroencephalogram (EEG), computerised tomography scan (CT) or magnetic resonance imaging (MRI), Carotid Doppler ultrasound scan, blood pressure monitoring, and echocardiogram and a tilt table test are used to investigate recurrent episodes of syncope.

Ultimately if no diagnosis can be made a small ECG recorder can be inserted under the skin (Implantable loop recorder Reveal Medtronic TM) so that ECGs can be recorded continuously for 18 months.

How can syncope be treated?

Generally, syncope is treated at the time of fainting by lying down and raising the legs in order to improve blood flow to the brain.

Treatment for an underlying cause may be necessary in order to stabilise and reduce the number of syncope episodes.

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